1. Field of the Invention
The present invention relates to an optical disc apparatus accessing method and system therefor capable of reproducing an optical disc on one surface of which are provided plural layers of information recording surfaces.
2. Description of the Prior Art
In the optical disc as a recording medium, laser discs (LD) have been extensively popularized as media in which plural layers of information recording surfaces are provided. In these recording media, each layer of information recording surface is present on both surfaces of the media in terms of physical construction. Therefore, in the case where information recording layers to be reproduced need be switched, it is general that the disc is inverted or changed.
With the recent trend of larger capacity of data for a computer and practical use of recording and reproducing of digital moving picture information, it has been demanded to make the optical disc higher recording density. The specification of a large capacity optical disc such as DVD (Digital Versatile Disc) has been proposed, and an optical disc such as a dual-layer disc has been standardized in addition to a conventional information recording of a one-side single layer. Since these optical discs have a dual-layer information recording layer on one side, there is necessary a reproducing method different from the conventional reproduction of single layer disc depending on switching of an information recording layer to be reproduced, and the form of information recorded and how to use it. One method is an accessing method and the other is a pausing (temporary stop) method.
In the optical disc, in the case where an optical pickup is accessed to a recording position of read target information on the same information recording layer in order to realize the high speed access, normally, present position information recorded in the disc is first read to obtain the present position of the optical pickup. Then, a target position is obtained from a logic or physical address of read target information. These two positions are converted from an information recording format of the disc into physical position information, the distance on a disc plane between the two points is obtained, and the optical pickup is accessed to the target position by means for controlling a slider on which the optical pickup is loaded.
However, in the case of the optical disc having a plurality of information recording layers on one side, there is taken the procedure such that in the case where read target information is present on the other information recording layer, the track positions between the information recording layers are not always coincided, and the optical pickup is moved to the target position on the basis of position information of the information recording layer now being reproduced, after which the optical pickup is moved to the target information recording layer. This procedure has a problem in that accessing cannot be made to the target position at high speeds and accurately.
In addition, the one-side dual-layer disc of DVD includes two kinds, one being a parallel track path (hereinafter referred to as PTP) in which the recording path of the first layer is the same as that of the second layer as shown in FIG. 3 (1), and the other being an opposite track path (hereinafter referred to as OTP) in which the recording path of the first layer is reversed to that of the second layer as shown in FIG. 3 (2). In case of the OTP, the physical address of the second layer is provided without direct relation with that of the first layer, and therefore, accessing to the other information layer is impossible on the basis of the position information of the information recording layer now being reproduced.
Also, with respect to the pausing (temporary stop) operation, there is a problem in that the pausing is not obtained in the second layer of the disc of OTP in the state of the operation of the conventional reproduction of one-side single disc.